The present invention relates to a method and device for controlling a bidirectional stepping motor including a stator comprising an armature which has first, second and third pole faces defining therebetween a substantially cylindrical space and which comprises first and second magnetic circuits respectively connecting the first pole face to the second pole face and the first pole face to the third pole face, the stator further comprising first and second windings which are magnetically coupled to the first and second magnetic circuits respectively, and the motor further including a rotor comprising a permanent magnet mounted rotatably in said space.
A motor as defined above is described in German patent application laid open as DE 30 26 004A. In accordance with that application, the motor is controlled by current pulses which are simultaneously applied to the two windings, whenever the rotor is to rotate through one step, that is to say, 180.degree.. The polarity of the current flowing in one of the windings is reversed substantially at the middle of the drive pulse.
The level of power consumption of a motor which is actuated in the above-indicated manner is fairly substantial, since current flows simultaneously in the two windings. In addition, the fact that the polarity of the current in one of the windings has to change in the middle of the drive pulse means that the motor control circuit requires eight transistors which conventionally form two bridge assemblies of four transistors, each assembly being connected to one of the windings. The eight transistors which must carry a fairly strong current occupy a large surface area on the silicon chip in which all the components of the electronic circuit for producing the drive pulses are integrated.